Vibe Change Spec Skill

Handles scope changes at any point during the build — safely, in the right order. Always assesses impact first. Always waits for confirmation. Never edits files speculatively.

Always run in Plan Mode (Shift+Tab). Do not write any code in this skill.

The O'Reilly principle this enforces

Drift prevention — scope changes must be logged explicitly. An informal "just quickly add X" mid-task produces a codebase that doesn't match its documentation. When review: runs, it finds violations with no logged context. change: prevents this by stopping work, assessing impact, and updating all affected documents before building continues.

When this skill runs

Any time the user signals a scope change:

• change: add dark mode before we build screens
• change: remove social login — email only
• change: add push notifications to backlog
• change: promote push notifications to active
• change: rename "ideas" to "posts" throughout
• change: revert the PDF attachment change we made last week
• Natural language: "actually I also want X", "I forgot Y", "can we cut Z"

Step 1 — Understand the change

Extract:

• What is being added, removed, modified, renamed, or reverted
• Whether it's a new feature, requirement tweak, removal, rename, backlog op, or revert
• Whether it's urgent (insert now) or deferred (backlog)

If ambiguous, ask ONE clarifying question.

Confirm:

"Got it — you want to [add/remove/modify/revert] [X]. Let me check what this affects."

Step 2 — Read current state

Read in order. Skip files that don't exist — note their absence:

1. BRIEF.md (if exists) — original problem, core value, v1 feature set
2. vibe/ARCHITECTURE.md (if exists) — established patterns and principles
3. vibe/SPEC.md — what is currently in scope
4. vibe/SPEC_INDEX.md — feature list and state
5. vibe/TASKS.md — active work, done vs pending
6. vibe/PLAN.md — current architecture
7. vibe/CODEBASE.md — what has actually been built

If active feature or bug folder exists (from TASKS.md active block):

1. Active FEATURE_TASKS.md or BUG_TASKS.md

Step 3 — Assess impact

Build stage

Before any code — doc updates only. Zero retrofit. Between tasks — last task done, next not started. New tasks slot cleanly. Mid-phase — some tasks done. May need to pause and insert new tasks. Cross-phase — change affects already-built architecture or data layer. Retrofit needed. Post-completion — fully built and conformance-checked. Full retrofit + regression strategy.

Impact checklist

• [ ] Adds/removes feature from SPEC.md?
• [ ] Changes data model (table, field, relationship)?
• [ ] Changes any API endpoints already built?
• [ ] Affects screens or components already built?
• [ ] Changes architecture in PLAN.md?
• [ ] Changes patterns or conventions in ARCHITECTURE.md?
• [ ] Changes core value or feature set in BRIEF.md?
• [ ] Do tasks already marked [x] need retrofitting?
• [ ] Affects active feature/bug folder?
• [ ] Is this additive (now) or deferred (backlog)?

Feature map cascade check

If vibe/PLAN.md exists and has a Section 6 feature map — run this check:

Find the affected feature in the feature map.

Extract:

• depended_on_by — features that cannot start until this one is done
• shared_data — entities this feature creates that others consume
• parallel_candidates — features planned to run alongside this one

For each feature in depended_on_by:

• Is it already built? → retrofit risk, flag as cross-phase
• Is it planned but not built? → update its spec deps before it starts
• Is it in progress? → pause it, assess data model impact first

For each shared_data entity this change affects:

• Which downstream features read this entity?
• Does the change alter the entity schema? → all consumers need review
• Does the change remove the entity? → all consumers are now broken

Surface cascade clearly in Step 4:

Feature map cascade:
  ⚠️  [Feature X] depends on [changed feature] — [built/in progress/planned]
      Impact: [what breaks or needs updating]
  ⚠️  [Feature Y] reads [affected entity] — [built/in progress/planned]
      Impact: [schema change affects Y's data layer]
  ✅  [Feature Z] — no dependency on changed feature

If no feature map in PLAN.md — skip this check, note its absence.

Revert detection

If the change is reverting a previous scope change (e.g. "remove the PDF feature we added"):

• Find the original D-ID in DECISIONS.md
• Identify all tasks that were added or retrofitted at that time
• Assess which tasks have been completed since (those need retrofit to undo)
• Treat as a new scope change entry (not a deletion of the original D-ID)
• Run the feature map cascade check for the reverted feature too

Step 4 — Tell the user impact before touching anything

Change requested: [one sentence plain English]

>

Build stage: [Before code / Between tasks / Mid-phase / Cross-phase / Post-completion]

>

What this affects: - Spec: [what changes in plain English] - Tasks: [N new / M retrofit / K removed — plain English] - Code already built: [affected — what needs revisiting / not affected] - Architecture: [patterns affected / not affected]

>

Feature map cascade: [None / see cascade findings above] - [Feature X] — [built/planned] — [impact] - [Feature Y] — [built/planned] — [impact]

>

Effort: [Small — doc only / Medium — new tasks / Large — retrofit needed]

>

Recommendation: [Add to backlog / Insert before next task / Address now with retrofit]

>

Ready to proceed? (or "add to backlog instead")

Wait for confirmation. Never touch files before confirmation.

• "add to backlog" → jump to Step 11 (Backlog)
• "proceed" → continue to Step 5

Step 5 — Update vibe/SPEC.md + vibe/SPEC_INDEX.md

Always updated together — never one without the other.

Adding a feature: Add section with acceptance criteria. Add update note at top:

> ⚠️ Last updated: [date] · Scope addition: [what] · Build stage: [stage]

Removing a feature: Strikethrough — never delete:

~~## Feature: [Name]~~
> ⚠️ Removed: [date] · Reason: [why] · See DECISIONS.md D-[ID]

Modifying: Edit in-place, mark what changed:

> ~~Original: [old]~~
> Changed [date]: [new] — [reason]

SPEC_INDEX.md update: Update relevant entry. Update sync date.

Save both.

Step 6 — Update BRIEF.md (if exists)

If BRIEF.md doesn't exist — skip this step, note it in the user's summary.

BRIEF.md must reflect current reality — not the original idea.

Feature added/removed: Update v1 feature set table. Core value changed: Update core value section with change and reason. Stack changed: Update tech stack table. Always append:

- Scope change [date]: [what changed and why — one line]

Save updated BRIEF.md.

Step 7 — Update vibe/ARCHITECTURE.md (if affected)

Only if change affects: patterns, conventions, folder structure, state management, API design, testing philosophy, or tech decisions.

Add new pattern or update changed decision. Always add changelog line if updated:

> 📝 [date] · Scope change D-[ID] — [what changed architecturally]

Skip and state explicitly if no architecture impact.

Step 8 — Update vibe/PLAN.md (if affected)

Only if change affects: data model, API shape, architecture layers, or phase structure.

Add changelog line at top. Update relevant sections in-place. Skip and state explicitly if no impact.

Step 9 — Update vibe/TASKS.md

All TASKS.md updates in plain English. Task IDs stay for agent sequencing.

Adding new tasks — expand inline feature block, insert in correct sequence. Adding retrofit tasks — add HM-001-R style entries inline with plain English. Removing tasks — strikethrough inline with plain English reason. Reverting — add retrofit tasks for any completed work that needs undoing.

Always update "What just happened" and "What's next":

## What just happened
🔄 Scope change: [plain English — what changed and why]
   [N new tasks / M retrofits / K removed]

## What's next
⬜ [TASK-ID] · [plain English next task]
Say "next" to continue.

Step 10 — Update vibe/DECISIONS.md

---
### D-[ID] — [Short title]
- **Date**: [date] · **Type**: scope-change
- **Trigger**: change: command — user-initiated
- **Build stage**: [stage]
- **What changed**: [exact description]
- **Why**: [user's stated reason]
- **Before**: [original scope]
- **After**: [new scope]
- **Tasks affected**: New: [IDs] · Retrofit: [IDs] · Removed: [IDs]
- **Folders affected**: [feature/bug folders or "none"]
- **Architecture impact**: [Yes — what / None]
- **BRIEF.md updated**: [Yes / No — didn't exist]
- **Approved by**: human
---

Step 11 — Update vibe/CODEBASE.md (only if change affects built structure)

Update only if: the change removes/renames something built, or establishes a new pattern. Skip and state explicitly if no update needed.

Step 12 — Backlog (add now, build later)

Add to vibe/backlog/[YYYY-MM-DD]-[feature-slug].md:

# [Feature Name]
> Added: [date] | Status: deferred

## What
[Description]

## Why deferred
[Reason]

## Effort estimate
[Small / Medium / Large]

## Dependencies
[What must be done before this]

## Promote when
[Condition]

## Promote with
change: promote [feature-name] to active

Update SPEC.md Backlog section, SPEC_INDEX.md, and TASKS.md backlog section.

Promoting a backlog item

When user says change: promote [item] to active:

1. Read vibe/backlog/[date-slug].md
2. Run vibe-add-feature to generate the full feature kit

(tell user: "Running feature: to build the full spec and task list for this")

1. Update SPEC.md — move from backlog to active features
2. Update SPEC_INDEX.md
3. Mark backlog file as promoted (or delete it)
4. Log in DECISIONS.md as scope-change

Step 13 — Commit docs

# SPEC always — always paired:
git add vibe/SPEC.md vibe/SPEC_INDEX.md
git commit -m "docs(SPEC): [add/remove/modify] [what] — D-[ID]"

# TASKS + DECISIONS always:
git add vibe/TASKS.md vibe/DECISIONS.md
git commit -m "docs(TASKS+DECISIONS): scope change D-[ID] — [N new, M retrofit, K removed]"

# BRIEF.md if exists and changed:
git add BRIEF.md
git commit -m "docs(BRIEF): scope change D-[ID] — [what changed]"

# ARCHITECTURE.md if changed:
git add vibe/ARCHITECTURE.md
git commit -m "docs(ARCHITECTURE): [what changed] — D-[ID]"

# PLAN.md if changed:
git add vibe/PLAN.md
git commit -m "docs(PLAN): [what changed] — D-[ID]"

# Active feature/bug folder if changed:
git add vibe/features/[date-slug]/FEATURE_TASKS.md
git commit -m "docs(FEATURE_TASKS): scope change D-[ID] — [feature]"

# CODEBASE.md if changed:
git add vibe/CODEBASE.md
git commit -m "docs(CODEBASE): [what changed] — D-[ID]"

# Backlog if created:
git add vibe/backlog/[date-slug].md
git commit -m "docs(BACKLOG): add [feature-name] — deferred [date]"

Step 14 — Hand off to user

✅ Scope change complete.

**What changed:** [plain English — one or two sentences]
**Your task list is updated** — open vibe/TASKS.md to see the new sequence.
**Next task:** [plain English]

Say "next" to continue building.

No session phrases. No file paths. Human readable only.

Quick reference — change types and files touched